In the commonly assigned application of Shekleton et al, filed Dec. 28, 1988, entitled Gas Turbine Annular Combustor with Radial Dilution Air Injection, Ser. No. 291,041 and assigned to the same assignee as the instant application, the details of which are herein incorporated by reference, there is disclosed a gas turbine construction wherein the vast majority of dilution air is passed completely around an annular combustor to cool the same and to impinge upon a turbine wheel shroud to likewise provide cooling. The dilution air is then injected into the combustor outlet just upstream of the turbine nozzle to mix with the gases of combustion before contacting the nozzle. An extremely compact assembly results. Moreover, the assembly is capable of relatively high power densities without accelerated failure rates because of the excellent cooling of the turbine shroud that is obtained which in turn reduces thermal stresses in the apparatus.
Nonetheless, further improvement is desired so as to achieve the maximum utility of the system. In particular, for maximum utility, such a system must have uniform airflow about the combustor. Typically, the airflow will be from the turbine compressor about the radially outer side of the annular combustor and then about a radial wall of the combustor opposite from the combustor outlet and finally, about the radially inner wall of the combustor whereat the dilution air further impacts against the turbine shroud. If this airflow is not uniform, hot spots may develop. Hot spots are, of course, to be avoided because the resulting thermal gradients induce thermal stresses due to the temperature differences.
In a system of the type mentioned, it is extremely important that uniform airflow be present in the area adjacent the turbine shroud and where the dilution air stream is combined with the gases of combustion just upstream of the nozzle. Not infrequently, vanes will be employed in this area to direct the flow of the dilution area in a given path and if flow through the vanes is not uniform, hot spots will result. These in turn will result in distortions that may further change the shape of the passage for the airflow, which in turn increases the nonuniformity of airflow, which leads to greater distortions, etc.
The present invention is directed to overcoming one of more of the above problems.